Thermodynamic and Kinetic Study of Rhodamine B Dye Removal from Aqueous Solution by a GO–γ-Al2O3 Nanocomposite

A GO–γ-Al₂O₃ nanocomposite containing 10 wt% graphene oxide (GO) and 90 wt% γ-Al₂O₃ was investigated for the removal of Rhodamine B (RhB) from aqueous solution using a batch adsorption process. γ- Al₂O₃ nanoparticles were prepared by a co-precipitation method followed by calcination at 550°C, while GO was synthesized using a modified Hummers method. The prepared materials were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). The investigated adsorption variables included contact time, adsorbent dosage, pH, initial dye concentration, and temperature. Under the reported experimental conditions, the highest RhB removal was obtained at pH 3 and an adsorbent mass of 0.15 g after 60 min. Kinetic data were evaluated using pseudo-first-order and pseudo-second-order models, and the pseudo-second-order model provided the better fit according to the reported statistical criteria. Equilibrium data were evaluated using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. Thermodynamic parameters were recalculated using an explicitly defined dimensionless standard-state equilibrium constant.